1. Field of the Invention
The present invention relates generally to the fields of interlocks and more particularly to a mechanical door interlock for an electrical equipment enclosure. The interlock enables the door to be opened only when the electrical apparatus is in a predetermined condition and prevents the condition of the electrical apparatus from being changed when the door is open.
2. Description of the Related Art
Various door interlocks for electrical equipment enclosures are known. In typical applications, the interlock is associated with a switch in order to permit the door to be opened only when the switch is open, and to prevent the switch from being closed while the door is opened. Reference may be made to the following U.S. Patents for examples of interlocks: U.S. Pat. Nos. 4,405,844; 4,073,000; 3,790,861; 3,748,621; 3,339,118, 4,118,607; 4,034,169; 3,991,291; 3,882,291; 3,778,567; 3,296,393; and 3,385,938.
Considering the structure and operation of the interlock of commonly assigned U.S. Pat. No. 4,405,844 and referring to FIG. 3B of that patent, with the switch in the closed position, the locking arm 58 is incapable of pivoting due to the position of a cam 50 carried by the switch shaft 38. The locking arm 58 is connected to a cam follower 100 via a wire 65 of a control cable 65. Since the locking arm 58 is incapable of pivoting, the cam follower 100 is also unable to pivot clockwise under the spring bias of a spring 108. Accordingly, the door latch 116 is maintained in a doorlatching position since the portion 120 of the door latch 116 is prevented from pivoting due to the interaction of the projection 102 on the cam follower 100. Additionally, with the door opened, the switch cannot be closed due to the stud 62 of the locking cam 58 preventing rotation of the cam 50 affixed to the switch shaft 38.
While the various interlocks of the prior art may be generally suitable for their intended uses and respective enclosures, it would be desirable to provide a new interlock that is suitable for a new door-latching system; i.e., an interlock that incorporates an appropriate design for a door-latching arrangement which includes a rotatable shaft which drives latching hooks into engagement about latch pins.